MTU/MSS Calculator

SanchitGurukul Networking Tools

MTU/MSS Calculator

Calculate TCP MSS from an MTU, estimate effective MTU after encapsulation overhead, and identify fragmentation-safe values.

Calculator inputs

bytes

Calculated results

Original link MTU 1500 bytes
Total encapsulation overhead 0 bytes
Effective IP MTU 1500 bytes
Recommended TCP MSS 1460 bytes
ICMP ping payload test 1472 bytes

Formula

Effective MTU = Link MTU − Encapsulation overhead

MSS = Effective MTU − IP header − TCP header

Ping payload = Effective MTU − IP header − ICMP header

Standard Ethernet result

An IPv4 MTU of 1500 normally uses an MSS of 1460 bytes with a standard 20-byte TCP header.

Common reference values

Connection typeTypical MTUIPv4 MSSIPv6 MSS
Standard Ethernet150014601440
PPPoE149214521432
Common VPN-safe value140013601340
IPv6 minimum MTU128012201220

Note: Actual IPsec, GRE, VXLAN, and VPN overhead varies with protocol options, encryption, authentication, NAT traversal, and outer IP version. Validate with packet capture or a “do not fragment” ping test.

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